1. Field of the Invention
This invention resides in the area of grand piano key and hammer actions and more particularly relates to a grand piano action with an improved adjustable friction hammer flange pivot design.
2. Description of the Prior Art
To a pianist, it is important that the pressure required to depress the piano keys feel uniform across the keyboard. If every key feels alike, the pianist can exert greater control over the volume of the musical tones produced, making the piano easier to play as well as allowing the pianist to play more expressively. For instance, if each key requires the same pressure to produce a given volume, the pianist can easily play a series of notes at the same volume by applying the same pressure to each key. If, on the other hand, each key requires a different pressure to produce a given volume, the pianist has the difficult task of learning how much pressure to apply to each key at a particular piano in order to play a series of notes at the same volume. Therefore it is considered desirable to build a piano action so that there is uniform "feel" in each key.
The grand piano is a stringed keyboard instrument which uses a key-activated mechanical system called an "action" to produce musical tone of varied intensity from the strings and soundboard.
Grand piano actions typically have a keyboard consisting of eighty-eight keys. Each key consists of a series of wooden pivots and levers designed so that the pianist can strike the key and thereby propel the piano hammer into the strings with force sufficient to create musical tone from the strings and soundboard. Specifically, each key has three pivoted levers: the hammer shank, the wippen, and the key lever. When the key is at rest, the weight of the hammer shank, with its attached hammer and knuckle, rests on top of the wippen which in turn rests on top of the back side of the key lever at the capstan. The weight of the action parts on the back side of the key causes the iron of the key, pivoted on the balance rail, to rest in an elevated position such that the bottom side of its proximal end is approximately three-eighths of an inch above the front rail. For the piano action to work properly, there must be sufficient weight on the back side of the key so that the force of gravity can act to return the front side of the key to its rest position after being depressed.
To play a note, the pianist strikes downwards with his finger against the upper proximal surface of the key, causing the front of the key to move downwards. As the front of the key moves down, the key pivots at the balance point, causing the back end of the key to move upwards, pushing up the wippen and hammer shank with its attached hammer thereby propelling the hammer into the string, creating a musical tone. When released, the key comes to rest in its former position with the lower side of its proximal end three-eighths of an inch from the front rail.
The ability to create musical tone of varied volume is of primary importance to the pianist. In order to play specific levels of volume, the pianist has to be able to control precisely the speed of the hammers as they strike the strings. The pianist senses how fast the hammer is being propelled to the string by feeling how much pressure is exerted against the key as it is depressed. The greater the pressure, the higher the volume of the tone produced.
When depressing a key, the pianist feels a certain amount of force from the weight of the parts. In addition, the pianist feels a significant force of resistance resulting from friction between the moving parts of the action. In other words, the resistance that is felt in the key has both a weight component and a frictional component.
Manufacturers of pianos are careful to make the weight of the action parts uniform. In this way they can make the weight component of key resistance reasonably uniform. However, the frictional component of key resistance is more difficult to control. Friction causes problems in piano actions because it changes frequently and unpredictably, both daily and seasonally, due to such factors as changes in humidity and wear of parts. When friction changes, the key resistance changes.
Unstable friction is an inherent trait of piano actions because to this date the only material found suitable for the fabrication of action parts is high-grade, well-seasoned hardwood. Even the most well-seasoned wood, however, will expand and contract under varied conditions of climate and humidity. Unfortunately the effects of this expansion and contraction are unpredictable and cause friction in the action pivots to change unpredicably. Because friction changes unpredictably, the frictional component of key resistance invariably becomes non-uniform from key to key, making the action feel uneven to the pianist. Keeping friction at a constant level, in order to maintain uniform key resistance, is a major problem for piano makers.
In particular, the hammer shank pivot has a major influence on friction levels in the action. If a hammer shank pivot becomes tight, it will have the effect of making the key feel sluggish and difficult to press. If it is too loose, the key plays too easily and the pianist has difficulty sensing the movement of the hammer, making it difficult to control the action. Actions with low friction tend to be difficult to control, akin to driving a car with no brakes. Pianists like to play on actions which have a certain degree of friction, not too much or too little.
The friction level in each key can be controlled by adjustment of the friction in the hammer flange pivot. Heretofore, the methods used for controlling friction in the hammer shank pivots have proven to be impractical. In the past, piano manufacturers have tried to solve the friction problem with the aid of adjustable friction hammer flange pivot designs. There exist a number of hammer shank pivot designs which utilize a screw adjustment for adjusting friction levels in the hammer flange pivot to variably tighten against the brass pin retaining the bifurcated hammer shank. This approach is theoretically highly desirable because levels of frictional resistance can be individually adjusted and maintained in each key by simply turning a screw. However, the adjustable friction hammer pivot designs heretofore tried have been unsuccessful.
In the mid-nineteenth century it was common to find square grand pianos with actions that used a type of hammer shank pivot which had an adjustment screw bearing against the pin which could be tightened or loosened, thereby raising or lowering the friction in the pivots. However, this design is not compatible with the type of action currently used in grand pianos. Also, it was difficult to accurately control friction with this design, and the design was complicated and expensive to produce due to the small screws and area of insertion. Also the design is generally incompatible with today's design requirements.
Erard, the French piano-making firm, utilized a similar type of adjustable friction hammer shank pivot in the pianos it produced during the nineteenth century. Later its use was discontinued. The Erard adjustable hammer shank pivot was used in an action design that is similar to today's grand piano action. In fact, the modern piano action evolved out of the design of the Erard action which was invented in 1829 by Sebastian Erard. However, the design of the Erard adjustable friction hammer shank pivot was not readily adaptable to the design requirements of the modern action because of the orientation of its components. It was expensive to produce and because it was made of brass, it was prone to failure from metal fatigue. Also, it was difficult to turn the adjustment screw in order to effect a fine degree of control of the level of friction in the pivot.
By the latter part of the nineteenth century, all grand piano makers had adopted the same system for making hammer shank pivots in which system the friction parameters of the pivots are set in the factory. This system is stil in general use today. It utilizes a wooden hammer shank with a bifurcation on the shank side. In both sides of the bifurcation are drilled small holes which are lined with felted wool cloth. The bifurcated portion of the hammer shank fits around a wooden flange which is fixed on the hammer flange rail. A hole is drilled in the flange such that it lines up with the cloth-lined holes in both sides of the bifurcated hammer shank end. A brass pin is then inserted through all three holes and cut off flush on the outer side of each fifurcated hammer shank end. The hole in the flange is drilled undersize so that the brass pin will be held generally non-rotatably therein. Friction is preset in the factory by matching the size of the pin with the cloth-lined holes in each bifurcated hammer shank end such that the hammer shank is held securely to the hammer flange while still being able to rot ate freely around the axis of the brass pin. Presetting friction requires a high degree of skill on the part of the workers responsible for assembling parts in the factory.
The problem with this system of "presetting" friction comes from the fact that the friction levels as set in the factory do not remain constant after the parts are assembled. If friction in the action pivots changes, the only way to reset the friction is to disassemble the parts and rematch the brass center pins with the cloth holes. This procedure is time-consuming and costly and still does not guarantee frictional stability. Once repaired, friction levels will still change under various conditions of use.
As a result, manufacturers of pianos tend to address only the most visible problem associated with action friction, namely sluggish or stuck keys resulting from high friction, by reducing friction in the hammer shank pivots to a minimum during the manufacturing process. In addition, dry lubricants such as graphite or teflon are often added to the cloth in the hammer shank pivot in order to try to prevent pivots from becoming tight. This practice may help reduce the chances of hammer shank pivots becoming tight, but it does not eliminate frictional changes. Also, this approach tends to produce actions that don't have enough friction.
The shortcomings of the hammer shank pivot frictional control designs previously used and the drawbacks of the system now in general use by piano manufacturers demonstrate the need for a practical hammer shank pivot design which allows for quick and easy adjustment of friction, thereby allowing for compensation of friction levels in each key in order to maintain a uniform "feel" to the piano's action. Today's manufacturers of pianos have given up on the concept of adjustable hammer shank friction as impractical.